Title of Invention

A PROCESS FOR PREPARATION OF NOVEL EPOXY RESIN THERMOSET MATERIAL

Abstract

The present invention relates to a process for preparation of novel epoxy resin thermoset material. The curing agent in this invention is polyaniline sulfate and the thermoset matrix may be epoxy resin. The novel epoxy resin - polyaniline sulfate composite is prepared using emulsion polymerization process, wherein the epoxy resin - polyaniline sulfate composite is in organic carrier solvent and or as a single component material. The process steps are: polymerizing aromatic amine in the mixture of aqueous and hydrocarbon solvents in the presence of anionic surfactant, initiator and epoxy resin 0.45 to 37.5 gram for 2.3 ml of aniline in the temperature range -5 to 40°C for 4 hrs, separating the epoxy resin -polyaniline sulfate composite by conventional method from the reaction mixture, evaporating the solvent and heating the composite at a temperature in the range of 180 to 315°C to get the epoxy thermoset material.

Full Text

The present invention relates to a process for preparation of novel epoxy resin thermoset material. The present invention particularly relates to epoxy resin thermoset material and methods for preparing them. Accordingly, the curing agent in this invention is polyaniline sulfate and the thermoset matrix may be epoxy resin. The present invention, more particularly relates to a process for preparing epoxy resin - polyaniline sulfate composite using emulsion polymerization process, wherein the epoxy resin - polyaniline sulfate composite is in organic carrier solvent and or as a single component material. The preparation of epoxy resin thermoset material was carried out by evaporating the organic solvent and heating the epoxy resin - polyaniline sulfate composite at high temperature. Epoxy resins were first introduced commercially in the United States around 1950 and since then their use has grown rapidly. They are the major industrial plastic capable of undergoing a large variety of addition and polymerization reactions leading to numerous thermoplastic and thermosetting forms. Epoxy resins may be broadly defined as resinous intermediate materials which are characterized by the presence of the epoxy group. Epoxy resin may also be defined as any molecule containing one or more alpha epoxy groups. When treated with the curing agent the thermosetting resins become hard, infusible system having different chemical and physical properties. Epoxy resins have varied industrial applications. They are used in protective coatings, adhesives for most substrates, body solders and caulking compounds, flooring, tooling compounds for moulds, stamping dies and patterns, forms, potting and encapsulation compound, low pressure molding resins and glass reinforced plastics. In general, epoxy resins are not used by themselves but rather they require the addition of a curing agent or hardener to convert them into a thermoset material. Depending on the chemical structure of the curing agent and curing conditions, it is possible to obtain toughness, chemical resistance, mechanical properties ranging from extreme flexibility to high strength and hardness, high adhesive strength, good heat resistance and high electrical insulation. Uncured resins range from low viscosity liquids to tack free solids, that along with the curing agents afford the fabricator a wide range of processing conditions. A relatively large number of chemical reagents are available or known to have utility as the curing agents or hardeners which may be added to epoxy resins to convert them to thermoset materials. It is also known that in the curing process both the epoxy and the hydroxyl groups of the resin may be involved. With the available curing agents the curing may be accomplished at room temperature or upon heating. It may take place in general either by a coupling or addition process, or by catalytic polymerization. The known curing agents or hardeners for epoxy resins fall into three categories: (1) the acidic type, for example, acid anhydrides; (2) aldehyde condensation products, for example, phenol-, urea-, and melamine- formaldehyde resins; and (3) amine type, for example, aliphatic and aromatic amines, polyamides, tertiary amines, and amine adducts. In the present invention, polyaniline is used as the curing agent for curing the epoxy resin. Polyaniline falls under the category of electrically conducting polymers and this field has got Nobel Prize in Chemistry for the year 2000. Electrically conducting polymers are subjected to in-depth research worldwide. These polymers offer the possibility of replacing metallic conductors and semiconductive materials in a variety of applications including batteries, transducers, switches, photocells, circuit boards, heating elements, antistatic protection (BSD) and electromagnetic protection (EMI). Conducting polymers possess the following advantages over metals: light weight, advantageous mechanical properties, good corrosion resistance and lower cost of synthesis and fabrication. The benefits of intrinsically conducting plastics include easy modification of their conductivity as a function of doping conditions which is particularly accentuated in conjunction with low conductivities. Exemplifying kinds of intrinsically conducting polymers are polyacetylene, poly-p-phenylene, polypyrrole, polythiophene and polyaniline. The use of most intrinsically conducting plastics in the promising applications mentioned above is, however, limited by the inferior processability and stability properties of these polymers. A technically and commercially promising intrinsically conducting polymer is polyaniline and its derivatives. Polyaniline is recognized as being chemically stable and electrically conductive in the protonated form. Nevertheless, the use of polyaniline has been limited because it has been considered intractable or unprocessible. A process has been developed for preparation of processable polyaniline-sulfate salt by emulsion polymerization method (Indian Patent Application NO. 295/DEL/2000 dated 23rd March, 2000 - the cited reference describes the status of preparation of polyaniline salts by aqueous and emulsion polymerization process). In the present process, epoxy resin - polyaniline sulfate composite was prepared using emulsion polymerization process, wherein polyaniline sulfate is used mainly to cure the epoxy resin. The present method involves a process for preparing epoxy resin - polyaniline composite using emulsion polymerization process, wherein the epoxy resin - polyaniline sulfate composite is in organic carrier solvent. The present method also involves the preparation of epoxy resin thermoset material. The main object of the present invention is to provide a process for preparation of novel epoxy thermoset material. The other object of the present invention is to provide a process for the preparation of epoxy resin - polyaniline sulfate composite using emulsion polymerization process, wherein the epoxy resin - polyaniline-sulfate composite is in organic carrier solvent. Another object of the present invention is to provide a process for the preparation of epoxy rising - polyaniline sulfate composite as a single component material, wherein polyaniline sulfate is the curing agent. Yet another object of the present invention is to provide a process for the preparation of epoxy resin thermoset material using polyaniline as a curing agent. Accordingly the present invention provide a process for preparation of novel epoxy resin thermoset material which comprises; polymerizing aromatic amine in the mixture of aqueous and hydrocarbon solvents in the presence of anionic surfactant, initiator and epoxy resin 0.45 to 37.5 gram for 2.3 ml of aniline in the temperature range -5 to 40°C for 4 hrs, separating the epoxy resin - polyaniline sulfate composite by conventional method from the reaction mixture, evaporating the solvent and heating the composite at a temperature in the range of 180 to 315°C to get the epoxy thermoset material. The present invention is directed to a process for the preparation of epoxy resin - polyaniline sulfate composite in non aqueous organic carrier solvent or a single component material. The present invention is also directed to a process for the preparation of epoxy resin thermoset material using polyaniline as curing agent. In an embodiment of the present invention, the aromatic amine used may be aniline. In an another embodiment of the present invention, epoxy resin may be the epoxy resin component having at least one 1,2-epoxy group per molecule. Mixtures of epoxy compounds having one epoxy functionality and two or more epoxy groups are also suitable. The epoxy compounds having two or more epoxy groups per molecule means that the nominal functionality is two or more. Generally, epoxy resins contain a distribution of compounds with a varying number of 1,2-epoxy equivalency. The actual average functionality of these epoxy compounds is about 1.5 or more. The epoxy compounds can be of the glycidyl ether type prepared by reacting epichlorohydrin with a compound containing at least one aromatic hydroxyl group carried out under alkaline reaction conditions. Examples of other epoxy resins suitable for use in the invention include diglycidyl ethers of dihydric compounds and epoxy novolacs. In an another embodiment of the present invention, the hydrocarbon solvent used may be chlorinated solvent selected from chloroform, dichloromethane, aromatic hydrocarbon selected from toluene. In yet another embodiment of the present invention, the anionic surfactant used may be selected from sodium lauryl sulfate, sodium octyl sulfate, dodecyl benzene sulfonic acid sodium salt. In still yet another embodiment of the present invention, the radical initiator used may be selected from ammonium persulfate, sodium persulfate. In one of the embodiment of the present invention, the reaction may be carried out in the temperature range 5 to 30CC. In one of the embodiment of the present invention, the amount of epoxy resin varied from 0.45 g to 37.5 g for 2.3 ml of aniline. The novelty of the invention lies in curing the epoxy resin using polyaniline-sulfate as an agent. A novel process for preparing epoxy resin - polyaniline composite using emulsion polymerization process, wherein the epoxy resin - polyaniline sulfate composite is in organic carrier solvent and or a single component material. The method also involves the preparation of novel epoxy resin thermoset material using polyaniline as a curing agent. These embodiments will be apparent from the ensuing detailed description of the present invention. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. EXAMPLE 1 Preparation of polyaniline - sulfate In a typical experiment, 2.3 ml of aniline was dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15-20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, filtered and finally washed with acetone. The sample was dried in atmosphere till it attained a constant weight. Weight of polyaniline sulfate obtained was 1.5 g. EXAMPLE 2 Preparation of epoxy resin- polyaniline sulfate composite using chloroform solvent at 30°C. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15-20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent chloroform and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 3 Preparation of epoxy resin- polyaniline sulfate composite using chloroform solvent at 20°C. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15-20 min. interval) at 20°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent chloroform and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 4 Preparation of epoxy resin- polyaniline sulfate composite using chloroform solvent at 5°C. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15 - 20 min. interval) at 5°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent chloroform and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 5 Preparation of epoxy resin - polyaniline sulfate composite using dichloromethane solvent. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml of dichloromethane. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15 - 20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent such as dichloromethane and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 6 Preparation of epoxy resin - polyaniline sulfate composite using toluene solvent. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml of toluene. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15-20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent such as toluene and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 7 Preparation of epoxy resin - polyaniline sulfate composite using anionic surfactant sodium octyl sulfate. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.2 g sodium octyl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.71 g of ammonium persulfate was added drop wise (15-20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent such as chloroform and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 8 Preparation of epoxy resin - polyaniline sulfate composite using sodium persulfate initiator. In a typical experiment, 2.3 ml of aniline and 15.0 g of epoxy resin were dissolved in 60 ml chloroform. Then a 40 ml aqueous solution containing 1.44 g sodium lauryl sulfate was added slowly while stirring which give an emulsion. To this emulsion, 100 ml aqueous solution containing 5.95 g of sodium persulfate was added drop wise (15-20 min. interval) at 30°C and kept the reaction mixture for 4hrs. The reaction mixture was washed with water, separated the organic layer and repeated the washing with water for three times. The organic layer was isolated and kept under anhydrous sodium sulfate for 12 hrs. Filtered the organic layer, evaporated the organic solvent such as chloroform and obtained the epoxy resin - polyaniline sulfate composite sample. The epoxy resin-polyaniline sulfate composite was heated at 200°C for four hours to get the epoxy thermoset material. EXAMPLE 9 Different ratio of polyaniline-epoxy resin composite was prepared using the above procedure (example 2) by varying the amount of epoxy resin content as 0.45, 0.75, 1.5, 7.5, 15.0, 22.5, 30.0 and 37.5 g in the reaction mixture. The epoxy resin - polyaniline sulfate sample was subjected for differential scanning calorimetry measurement from 40°C to 350°C at a heating rate of 10°C/min and the results are reported in Table I. As a representative system, the differential scanning calorimetry thermograms of polyaniline sulfate-epoxy ratio 1 : 1 shows an exothermic peak 185°C. The value of exothermic peak maxima, staring, end temperatures, enthalpy change of the cure reaction and cure time were calculated and the results are included in Table I. TABLE I DIFFERENTIAL SCANNING CALORIMETRY THERMOGRAM RESULTS (Table Removed) Differential scanning calorimetry result showed that the peak maxima increases from 185°C to315°C with the increase of resin content from 1:1 ratio to 1:25. Also the curing time increase from 4.4 mins. to 9.8 mins with the increase of resin content. The enthalpy change of the curing reaction are included in Table I. Differential scanning calorimetry thermograms of the jjojyaniline : epoxy resins for the first two ratio (ratio of 1:0.3 and 1:0.5) showed that the curing is not proper. The above results indicate that the epoxy resin can be cured at around 180°C for 4.5 mins for 1:1 ratio. EXAMPLE 10 The sample prepared as given in example 2 was subjected for differential scanning calorimetry measurement from 40°C to 350°C at a different heating rates from 5, 10, 15, 20, 25 and 30 °C/min. The peak maxima, peak starting, ending temperatures, enthalpy change and cure time were calculated and the results are reported in Table II. TABLE II DIFFERENTIAL SCANNING CALORIMETRY THERMOGRAM RESULTS (Table Removed) Differential scanning calorimetry thermograms showed that the peak maxima increases with the increase of heating rates. The cure time was found to be nearly the same (around 7.2 mins.) and also the enthalpy change of the curing reaction ( around 370 J/g) except for the first case, i.e. 5°C/min. EXAMPLE 11 Isothermal differential scanning calorimetry thermograms were recorded for polyaniline : epoxy in the ratio 1:10 (sample prepared as given in example 2) at different temperatures and found that the cure time decreases as 11.4, 8.0, 6.2, 4.8 and 3.9 min. with increase in temperature 180, 185, 190, 195 and 200 °C respectively. EXAMPLE 12 Epoxy resin was cured with polyaniline-sulfate salt prepared according to Experiment II at 180°C. The three different epoxy resin-polyaniline composites prepared are in the ratio 1:5, 1:10 and 1:20. Thermogravimetric analysis (TGA) of the polymer samples was carried out using Mettler Toledo Star system in the presence of nitrogen atmosphere up to 800°C and at a heating rate of 10°C/min. The three cured samples were subjected to TGA measurements from 40 to 800 °C. Generally, a similar TGA thermograms were observed for the all the three samples. TGA thermogram shows that the cured sample is stable up to 265°C and undergoes 77 % weight loss around 480°C. The main advantages of the present invention are : (i) use of polyaniline sulfate as curing agent for curing epoxy resin, (ii) the preparation of epoxy resin - polyaniline sulfate composite in organic solvents which may be used for different types of coatings application, (iii) the preparation of polyaniline sulfate - epoxy resin composition as a single component material which may be used as it is without using any additives and (iv) catalyst/accelerators are not necessary to cure the epoxy resin. In view of the above, it will be seen that several advantages of the invention are achieved and other advantageous results attained. As various changes could be made in the above methods and compositions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. We Claim: 1. A process for the preparation of novel epoxy resin thermoset material which comprises; polymerizing aromatic amine in the mixture of aqueous and hydrocarbon solvents in the presence of anionic surfactant, initiator and epoxy resin 0.45 to 37.5 gram for 2.3 ml of aniline in the temperature range -5 to 40°C for 4 hrs, separating the epoxy resin - polyaniline sulfate composite by conventional method from the reaction mixture, evaporating the solvent and heating the composite at a temperature in the range of 180 to 315°C to get the epoxy thermoset material. 2. A process as claimed in claim 1, wherein the aromatic amine used is aniline. 3. A process as claimed in claims 1-2, wherein in the epoxy resin used is selected from epoxy resin component having at least one 1,2-epoxy groups per molecule. 4. A process as claimed in claims 1-3, wherein the hydrocarbon solvent used is chlorinated solvent selected from chloroform, dichloromethane or aromatic hydrocarbon selected from toluene. 5. A process as claimed in claims 1-4, wherein the anionic surfactant used is selected from sodium lauryl sulfate, sodium octyl sulfate or dodecyl benzene sulfonic acid sodium slat. 6. A process as claimed in claims 1-5 wherein the radical initiator used is ammonium per sulfate or sodium per sulfate. 7. A process for the preparation of novel epoxy thermoset material substantially as herein described with reference to the examples.

Documents:

1204-del-2000-abstract.pdf

1204-del-2000-claims.pdf

1204-del-2000-correspondence-others.pdf

1204-del-2000-correspondence-po.pdf

1204-del-2000-description (complete).pdf

1204-del-2000-form-1.pdf

1204-del-2000-form-19.pdf

1204-del-2000-form-2.pdf

1204-del-2000-form-3.pdf